Linear contrast agent detection through low frequency manipulation of high frequency scattering properties

In medical ultrasound imaging, contrast agents in the form of encapsulated gas bubbles are injected into the blood to enhance the scattered blood signal which is weak compared to the scattered tissue signal. Obtaining blood information is, from a medical diagnostic point of view, very helpful. Due to the strong linearly back-scattered tissue signal, contrast imaging today relies on the nonlinear scattering properties of the added gas bubbles. These harmonic techniques typically have important limitations in sensitivity, specificity, and image range resolution. The present paper proposes a new method applying the total scattered contrast signal for image reconstruction, thus largely overcoming the problems encountered in contrast harmonic ultrasound imaging techniques. In the new method, contrast signals and tissue signals are differentiated applying a simple pulse subtraction technique which cancels or significantly reduces the scattered tissue signal, whereas the scattered contrast signal, due to assisting transmitted low frequency pulses altering the acoustic scattering properties of the contrast agent, is preserved in this process. The main mechanism through which this imaging technique selects the contrast agent signal is the linear resonant properties of the contrast bubble and the new method is thus mainly a linear contrast agent detection technique.